Growth Of Scots Pine Research Articles

The effect of silver and copper nanoparticles on the growth and mycorrhizal colonisation of Scots pine (Pinus sylvestris L.) in a container nursery experiment

Abstract: Recent research points to the possibility of nanoparticles being used as fertilisers, growth stimulators, and promoters of plant resistance or pesticides. In this study, we sought to determine the influence of nanoparticles of silver and copper (AgNPs and CuNPs) on growth parameters and spontaneous mycorrhizal colonisation of roots in 2-year-old container-grown seedlings of Scots pine. Foliar applications of nanoparticles were made through two growing seasons, four times a season, at concentrations of 0, 5, 25 and 50 ppm. Comparisons of the ultrastructures characterising the needles, stems and roots of the treated or untreated pines were conducted with transmission electron microscopy (TEM). The deployed CuNPs stimulated mycorrhizal colonisation at all concentrations, although the growth of seedlings was only promoted at a concentration of 25 ppm. Higher concentrations of AgNPs (25 and 50 ppm) inhibited the formation of mycorrhizae, though the lowest concentration (5 ppm) produced an increase in both mycorrhizal colonisation and the dry mass of roots. The species of ectomycorrhizal fungi found were Thelephora terrestris, Suillus bovinus and Sphaerosporella brunnea. The TEM results comparing treated and control (untreated) needles revealed changes in the chloroplasts from lens-shaped to spherical. Furthermore, an increase in the number of plastoglobules and the presence of large osmophilic globules in the cytoplasm associated solely with the needles of pines receiving 50 ppm nanoparticles were observed. In contrast, ultrastructural changes in stems and roots associated with the applications of NPs were not found. Overall, the results indicated that CuNPs and AgNPs could be used as stimulators of growth in general, and mycorrhizal colonisation in particular, among container-grown Scots pines. However, further work is needed to determine their optimal doses and concentrations.

Post-drought Resilience After Forest Die-Off: Shifts in Regeneration, Composition, Growth and Productivity.

A better understanding on the consequences of drought on forests can be reached by paying special attention to their resilience capacity, i.e., the ability to return to a state similar to pre-drought conditions. Nevertheless, extreme droughts may surpass the threshold for the resilience capacity triggering die-off causing multiple changes at varying spatial and temporal scales and affecting diverse processes (tree growth and regeneration, ecosystem productivity). Combining several methodological tools allows reaching a comprehensive characterization of post-drought forest resilience. We evaluated the changes in the abundance, regeneration capacity (seedling abundance), and radial growth (annual tree rings) of the main tree species. We also assessed if drought-induced reductions in growth and regeneration of the dominant tree species scale-up to drops in vegetation productivity by using the Normalized Difference Vegetation Index (NDVI). We studied two conifer forests located in north-eastern Spain which displayed drought-induced die-off during the last decades: a Scots pine (Pinus sylvestris) forest under continental Mediterranean conditions and a Silver fir (Abies alba) forest under more temperate conditions. We found a strong negative impact of a recent severe drought (2012) on Scots pine growth, whereas the coexisting Juniperus thurifera showed positive trends in basal area increment (0.02 ± 0.003 cm2 yr-1). No Scots pine recruitment was observed in sites with intense die-off, but J. thurifera and Quercus ilex recruited. The 2012 drought event translated into a strong NDVI reduction (32% lower than the 1982–2014 average). In Silver fir we found a negative impact of the 2012 drought on short-term radial growth, whilst long-term growth of Silver fir and the coexisting Fagus sylvatica showed positive trends. Growth rates were higher in F. sylvatica (0.04 ± 0.003 cm2 yr-1) than in A. alba (0.02 ± 0.004 cm2 yr-1). These two species recruited beneath declining and non-declining Silver fir trees. The 2012 drought translated into a strong NDVI reduction which lasted until 2013. The results presented here suggest two different post-drought vegetation pathways. In the Scots pine forest, the higher growth and recruitment rates of J. thurifera correspond to a vegetation shift where Scots pine is being replaced by the drought-tolerant juniper. Conversely, in the Silver fir forest there is an increase of F. sylvatica growth and abundance but no local extinction of the Silver fir. Further research is required to monitor the evolution of these forests in the forthcoming years to illustrate the cumulative impacts of drought on successional dynamics.

The Impact of Climate Change and Strong Anthropopressure on the Annual Growth of Scots Pine (Pinus sylvestris L.) Wood Growing in Eastern Poland

Changes in annual tree ring width (TRW) and its size depends not only on the changing climate and natural stress factors such as extreme air temperatures, shortages in rainfall and excess rainfall during the growing season, but also on anthropogenic stress, including chemical compounds emitted to the atmosphere or lowering of the groundwater table caused by the operations of plants with high environmental impact. The purpose of this article is to assess the impact of meteorological conditions and anthropogenic factors on the size of annual growth of Scots pine tree-stands in the conditions of the climate of central-eastern Poland. On the basis of five created site chronologies in the vicinity of Zakłady Azotowe Puławy (nitrogen factories in Puławy) and using the moving correlation analysis and multiple regression analysis, a significant influence of temperature and precipitation conditions on the TRW size is proved. A significant, positive influence of air temperature on TRW was proved for the majority of chronologies created in the period of January–March, as well as in June, while it remained negative in May. The wide rings of Scots pines were formed when the precipitation of October and January (prior to the resumption of cambium activity) was lower than the average, and higher in April and in June–August. After including the anthropopressure factors in the regression equations, the description of the variability of the annual tree ring width was corrected. The coefficient of determination ranged from approx. 29% to even above 45% and was higher, on average by 10%, for all studied chronologies of Scots pine compared to the one calculated for constructed equations considering only meteorological conditions. The strength and direction of the impact of the independent variables (SO2, NH3, NOx) analysed on TRW mainly depended on the distance from the plants, as well as on the direction of inflow of industrial pollution to the stands examined. In light of the proven climate changes in central and eastern Poland, the growth conditions of pine stands will most likely deteriorate.

Quantifying the effect of persistent dryer climates on forest productivity and implications for forest planning: a case study in northern Germany

BackgroundForest management decisions are based on expectations of future developments. For sound decisions it is essential to accurately predict the expected values in future developments and to account for their inherent uncertainty, for example the impact of climate change on forests. Changing climatic conditions affect forest productivity and alter the risk profile of forests and forest enterprises. Intensifying drought stress is seen as one major risk factor threatening forest management in the north German lowlands. Drought stress reduces tree growth and vitality and might even trigger mortality. But so far, it is not possible to quantify effects of a persistent dryer climate on forest productivity at a level suitable for forest management.MethodsWe apply a well-established single-tree forest growth simulator to quantify the effect of persistent dryer climates on future forest productivity. We analyse the growth of Scots pine (Pinus sylvestris L.), European beech (Fagus sylvatica L.) and oak (Quercus robur L. and Quercus petraea (Matt.) Liebl.) in two forest regions in the north German lowlands for a time interval of 60 years until 2070. The growth response under three different climate projections is compared to a baseline scenario.ResultsThe results show clear differences in volume increment to persistent dryer climates between tree species. The findings exhibit regional differences and temporal trends. While mean annual increment at biological rotation age of Scots pine and oak predominantly benefits from the projected climate conditions until 2070, beech might suffer losses of up to 3 m3·ha–1·yr–1 depending on climate scenario and region. However, in the projection period 2051 to 2070 the uncertainty ranges comprise positive as well as negative climatic effects for all species.ConclusionsThe projected changes in forest growth serve as quantitative contributions to provide decision support in the evaluation of, for example, species future site suitability and timber supply assessments. The analysis of productivity changes under persistent dryer climate complements the drought vulnerability assessment which is applied in practical forestry in northwestern Germany today. The projected species’ productivity has strong implications for forest management and the inherent uncertainty needs to be accounted for.

Comprehensive Study of Reclaimed Soil, Plant, and Water Chemistry Relationships in Highly S-Contaminated Post Sulfur Mine Site Jeziórko (Southern Poland)

The aim of the work was a comprehensive study of the soils (pH, EC, SOC, NT, ST), surface waters (pH, EC, Ca2+ Mg2+, Na+, NO3−, SO42−, Cl−, HCO3−), and reactions of trees and herbaceous plants in the restored forest ecosystem of a former sulfur mine. Common birch and Scots pine growth reaction, vitality (according to IUFRO standards- International Union of Forest Research Organizations), nutrient supply (Na, K, P, Ca, Mg, K), and Calamagrostis epigejos (L.) Roth chemical composition (Na, K, P, Ca, Mg, K) were assayed. The chemistry dynamics (pH, EC, DOC, NT, Ca, Mg, and S at the beginning and end of the experiment) of soil leaching and the sulfur load leached from the sulfur-contaminated soil substrates were evaluated. The remediation effects of birch and pine litter were assayed in an experiment under controlled conditions. It was found that reclamation was effective in the majority of the post-mining site; however, hotspots with sulfur contamination reaching even 45,000 mg kg−1, pH < 2.0 and electrical conductivity (EC) of 6500 µS cm−1 were reported. Surface waters typically displayed elevated concentrations of sulfate ions (average 935.13 mg L−1), calcium ions (up to 434 mg L−1), and high EC (average 1797 µS cm−1), which was related both to sulfur contamination and the sludge lime that was used in neutralization. Calamagrostis epigejos was found to be a species that adapted well to the conditions of elevated soil salinity and sulfur concentration. It was observed that the application of organic matter had a significant beneficial impact on the chemistry of soil solutions, but did not show a remediation effect by increased sulfur leaching in a short-term study.

Scots pine radial growth response to climate and future projections at peat and mineral soils in the boreo-nemoral zone

This paper aims to study what influence different meteorological parameters have on the radial tree growth of Scots pine (Pinus sylvestris L.) in peat and mineral soils, as well as to make predictions of radial tree growth responses to changing climate based on various future climate projections. Four Lithuanian peatland complexes representing different geographical settings and hydrological conditions were studied. From each study site, two tree-ring width (TRW) series were derived, one from trees growing on peat soil and one from trees on mineral soil at the periphery of the peatland. The annual growth rings from trees grown on mineral soils, in different geographical regions in Lithuania, show synchronicity, whereas the correlation between the TRW series from different peatland sites was weak to absent. The main factor that explains radial tree growth at the mineral-soil sites was air temperature during early spring (February–March), which influences the onset and duration of the growing season. However, variations in radial tree growth on the peatland sites were also attributed to lagged hydrological responses relating to precipitation and evaporation over several years. Our future projections show that growth conditions for pine trees on mineral soils will improve in the twenty-first century in Lithuania following an increase of air temperature in early spring. The predictions for the trees growing on peat soils, however, rely on the groundwater-level changes governed by a combination of precipitation and evaporation changes. Towards the end of the twenty-first century, the groundwater level in most Lithuanian peatlands is expected to increase, which most likely will result in harsher growth conditions for the peatland trees. This assumption is, however, open for debate as the peatland trees appear to favour the current warming conditions. It may therefore be too early to precisely predict future growth responses for the peatland trees, but this study is a next step to better understand future climate dynamics and vegetation responses in the Baltic region.

Linking stem growth respiration to the seasonal course of stem growth and GPP of Scots pine.

Current methods to study relations between stem respiration and stem growth have been hampered by problems in quantifying stem growth from dendrometer measurements, particularly on a daily time scale. This is mainly due to the water-related influences within these measurements that mask growth. A previously published model was used to remove water-related influences from measured radial stem variations to reveal a daily radial growth signal . We analysed the intra- and inter-annual relations between and estimated growth respiration rates (Rg) on a daily scale for 5 years. Results showed that Rg was weakly correlated to stem growth prior to tracheid formation, but was significant during the early summer. In the late summer, the correlation decreased slightly relative to the early summer. A 1-day time lag was found of preceding Rg. Using wavelet analysis and measurements from eddy covariance, it was found that Rg followed gross primary production and temperature with a 2 and 3 h time lag, respectively.This study shows that further in-depth analysis of in-situ growth and growth respiration dynamics is greatly needed, with a focus on cellular respiration at specific developmental stages, its woody tissue costs and linkages to source–sink processes and environmental drivers.

Quantifying the effect of pine mistletoe on the growth of Scots pine

SummaryMistletoe infection results in substantial growth losses in mistletoe‐infected forests. This study reports and evaluates the results of retrospective analyses of radial growth of Scots pine (Pinus sylvestris) in relation to the level of infection of pine mistletoe (Viscum album ssp. austriacum). A total of 43 Scots pine trees were destructively sampled from different sites. Of these trees, 14 were uninfected and 29 were infected. Infection classes were determined using six‐class dwarf mistletoe rating system (DMRS). All needle and mistletoe biomass were removed completely and weighed for each sampled tree. Subsamples from needles and all mistletoe biomass were taken to the laboratory for oven‐dried weight determinations. Five‐cm‐thick wood discs were cut from the stem at the breast height (1.3 m) to determine annual basal area increment for the last 25 years. In addition to DMRS, new infection classes were created using mistletoe‐to‐needle biomass (MB/NB) ratio. The results showed that the radial growth losses could be as much as 41% to 64% at different infection levels. The rate of growth loss in relation to DMRS and MB/NB ratio was similar, but with a larger variability in DMRS values. The results showed that both DMRS rating and MB/NB ratio seem to be important for quantifying growth loss on Scots pine trees infected with mistletoe. The results of this study can also be invaluable in modelling the effects of mistletoe on the growth of Scots pine trees.

Sarıçam (Pinus sylvestris L.) ormanlarındaki silvikültürel uygulamalar için yapılmış bir meşcere sıklık diyagramı

Aim of study: Residual stand densities are commonly defined using basal area (m2 ha-1) (BA) and number of trees per hectare (TPH) when using even-aged silvicultural methods such as clearcutting and shelterwood methods in Scots pine (Pinus sylvestris L.) forests. However, it has been stated that absolute density measures such as BA and TPH are not the most useful indexes because growing space at a given BA or TPH varies with average tree diameter. Therefore, silvicultural management tools such as stocking charts (SC) and density management diagrams (DMD) have seemed to be more useful when allocating growing space to achieve a broad range of silvicultural objectives in even-aged stands. Given the importance of stand density on the regeneration success and growth of Scots pine, and given the shortages of absolute density measures (i.e. BA and TPH), a density diagram would be a useful tool for this tree species as well. Thus, in this study, a stand stocking diagram (SD) was developed for Scots pine stands. Material and Methods: Two published equations developed from open grown Scots pine trees, and from normal Scots pine stands were utilized to determine the minimum density of full site occupancy and the average maximum density, respectively. The form of the diagram follows Gingrich stocking chart. Main results: The A-line on the diagram represents the average maximum density where trees, on average, have the minimum growing space needed to survive. The B-line represents the lowest density where canopy closure can occur and is the minimum stocking necessary for full site occupancy or canopy closure. Consistent with a published Scots pine DMD, there is biological relevance and utility to the stocking diagram created in this study. Highlights: With the stocking diagram presented in this paper, regeneration and tending applications will be more practical in Scots pine forests because available growing space will be well-determined and utilized using the diagram.

Impact of warming, moderate nitrogen addition and bark herbivory on BVOC emissions and growth of Scots pine (Pinus sylvestris L.) seedlings.

The changing climate will expose boreal forests to rising temperatures, increasing soil nitrogen (N) levels and an increasing risk of herbivory. The single and interaction effects of warming (+2 °C increase), moderate N addition (30 kg ha-1 year-1) and bark herbivory by large pine weevil (Hylobius abietis L.) on growth and emissions of biogenic volatile organic compounds (BVOCs) from shoots of Scots pine (Pinus sylvestris L.) seedlings were studied in growth chambers over 175 days. In addition, warming and N addition effects on shoot net photosynthesis (Pn) were measured. Nitrogen addition increased both shoot and root dry weights, whereas warming, in combination with herbivory, reduced stem height growth. Warming together with N addition increased current-year shoot Pn, whereas N effects on previous-year shoot Pn were variable over time. Warming decreased non-oxygenated monoterpene (MT) emissions in June and increased them in July. Of individual MT compounds, α-pinene, δ-3-carene, γ-terpinene and terpinolene were among the most frequently responsive compounds in warming treatments in the May-July period. Sesquiterpene emissions were observed only from warming treatments in July. Moderate N addition increased oxygenated monoterpenes in May, and MTs in June and September. However, N addition effect on MTs in June was clearer without warming than with warming. Bark herbivory tended to increase MT emissions in combination with warming and N addition 3 weeks after the damage caused by weevils. Of individual compounds in other BVOC blends, herbivory increased the emissions of methyl-benzene, benzene and hexanal in July. Hence, though both warming and N addition have a potential to change BVOC emissions from Scots pines, the N effect may also be partly cancelled by warming. Furthermore, herbivory pressure in combination with climate warming and N addition may, at least periodically, increase BVOC release to the atmosphere from young Scots pine seedlings.

Temporal and Spatial Change in Diameter Growth of Boreal Scots Pine, Norway Spruce, and Birch under Recent-Generation (CMIP5) Global Climate Model Projections for the 21st Century

We investigated how climate change affects the diameter growth of boreal Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.), and silver birch (Betula pendula Roth) at varying temporal and spatial scales. We generated data with a gap-type ecosystem model for selected locations and sites throughout Finland. In simulations, we used the current climate and recent-generation (CMIP5) global climate model projections under three representative concentration pathways (RCPs) forcing scenarios for the period 2010–2099. Based on this data, we developed diameter growth response functions to identify the growth responses of forests under mild (RCP2.6), moderate (RCP4.5), and severe (RCP8.5) climate change at varying temporal and spatial scales. Climate change may increase growth primarily in the north, with a clearly larger effect on birch and Scots pine than Norway spruce. In the south, the growth of Norway spruce may decrease largely under moderate and severe climate change, in contrast to that of birch. The growth of Scots pine may also decrease slightly under severe climate change. The degree of differences between tree species and regions may increase along with the severity of climate change. Appropriate site-specific use of tree species may sustain forest productivity under climate change. Growth response functions, like we developed, provide novel means to take account of climate change in empirical growth and yield models, which as such include no climate change for forest calculations.

Functional diversity differently shapes growth resilience to drought for co‐existing pine species

AbstractQuestionsWhat are the differences in tree growth and resilience in response to extreme droughts between three co‐existing pine tree species? Are growth–resilience components more influenced by intrinsic (age, tree height) or extrinsic factors (mass effects or functional diversity of the neighbourhood)? Is the tree's vulnerability to drought buffered by the functional diversity of the surrounding plant community?LocationMediterranean forest, northeast Spain.MethodsTrees from three co‐existing pine species with different drought tolerances (Aleppo pine – Pinus halepensis Mill.; Black pine – Pinus nigra subsp. salzmannii (Dunal) Franco; Scots pine – Pinus sylvestris L.) were sampled. The average age of the studed pines was ~30 years. Radial growth from 1980 to 2015 was measured and the pines’ responses to the most severe recent droughts (2005 and 2012) were studied by relating different growth resilience components (Rt, resistance; Rc, recovery; RRs, relative resilience) with intrinsic (age and height) and extrinsic factors of the neighbouring community around each tree. The considered extrinsic factors were CWM and niche complementarity of tree (height), leaf (specific leaf area, leaf dry matter content) and wood (wood specific gravity) traits. The way in which these factors affected growth resilience to drought was assessed.ResultsFor the whole study period we found lower growth of Scots pine than Aleppo pine, but similar resilience components (except for higher Rt in 2005 for the former species). Despite each drought year resulting in distinct responses, the growth resilience to drought was mostly dependent on tree age for Aleppo pine, while functional diversity modulated a high percentage of the resilience variance of Scots pine. Black pine had an intermediate strategy. CWM explained, in general, less variance of the resilience components than functional diversity.ConclusionsThe positive effect of surrounding functional diversity on Scots pine could be related to a greater resistance to drought, likely due to improved resource acquisition favouring its performance at the dry limit of its distribution area. Intrinsic tree features, mass effects and functional diversity differently shape growth resilience to different droughts for co‐existing tree species.

Temporal interactions among throughfall, type of canopy and thinning drive radial growth in an Iberian mixed pine-beech forest

Many factors can influence tree growth over time such as different forest management practices, climate or tree-to-tree interactions, especially in mixed forests. We show in this work how the temporal growth patterns for Scots pine and European beech depend on thinning intensity (0%, 20% and 40% extraction of basal area), canopy type (pine–beech vs. pine patches), throughfall and their interactions. To fulfill this objective we monitored radial growth of both species using band dendrometers during a 6-year long period including two very dry years. Temporal growth patterns differed between both species. Whereas Scots pine showed two main peaks of growth in May–June and October, European beech mainly grew from May to early September even when throughfall was very limited. Effects of thinning on growth generally increased for both species during dry periods both at the seasonal and annual scales. The treatment with 20% of thinning intensity was the most effective at the annual scale for enhancing growth of both species. However, increases in growth due to thinning were much higher in beech than in pine and lasted longer. Thinning effects on pine were higher in mixed canopy than in pure canopy and appeared to be modulated by throughfall. Global differences in pine growth between canopy types as a function of throughfall increased during the main growing season as beech canopy developed. Growth of Scots pine, but not that of European beech, generally increased with throughfall which suggests that pine might be more dependent for its growth on water from the soil surface layer while beech would depend more on water from deeper soil layers. Our findings have implications to select the most convenient thinning treatments and canopy type under a potential climate change scenario characterized by warmer conditions, more severe droughts and less throughfall.

Spatio-temporal variability in Scots pine radial growth responses to annual climate fluctuations in hemiboreal forests of Estonia

In this study, we used a comprehensive tree-ring network from Estonia and investigated Scots pine (Pinus sylvestris L.) radial growth responses to changing climate conditions, considering differences in site conditions and local climates. To assess whether climate influences Scots pine radial growth consistently across the country, we developed thirteen tree-ring width chronologies for pine populations growing in four forest site types – Cladonia, Calluna, Myrtillus, and Rhodococcum – in four sub-regions of Estonia and compared these to climate data. A correlation analysis between ring-width indexes and monthly resolved temperature and precipitation applied over the period of 1955–2006 revealed significant positive correlations with winter/early spring temperatures and the total precipitation of late summer in the year prior to growth. High mean temperatures in August of the year prior to growth were negatively related to pine growth, particularly on islands and in the Northeast of Estonia. Scots pine growth on mesic and medium fertile Myrtillus and Rhodococcum sites in the Southeast exhibited greater sensitivity to mean February−April temperatures, while high temperatures and low precipitation at the end of the summer of the previous growing season limited radial growth of pine on the islands and in the North-eastern sub-region. A principal component analysis conducted on mean index chronologies and a hierarchical cluster analysis performed on bootstrapped correlation coefficients showed that local climate is the main driver of common growth, followed by ecological site conditions. A moving correlation analysis, performed over the period of 1955–2006, using 30-year windows shifted by one year showed that climate-growth relationships are not stable in changing climatic conditions. Associations between Scots pine tree-ring width and winter temperatures are getting weaker.

Autumn versus spring planting: the initiation of root growth and subsequent field performance of Scots pine and Norway spruce seedlings

Autumn versus spring planting: the initiation of root growth and subsequent field performance of Scots pine and Norway spruce seedlings

Models for diameter and height growth of Scots pine, Norway spruce and pubescent birch in drained peatland sites in Finland

The aim of this study was to develop individual-tree diameter and height growth models for Scots pine, Norway spruce, and pubescent birch growing in drained peatlands in Finland. Trees growing in peatland sites have growth patterns that deviate from that of trees growing in mineral soil sites. Five-year growth was explained by tree diameter, different tree and stand level competition measures, management operations and site characteristics. The drainage status of the site was influencing growth directly or in interaction with other variables. Site quality had a direct impact but was also commonly related to current site drainage status (need for ditch maintenance). Recent thinning increased growth of all species and former PK fertilization increased growth of pine and birch. Temperature sum was a significant predictor in all models and altitude for spruce and birch. The data were a subsample of the 7th National Forest Inventory (NFI) sample plots representing northern and southern Finland and followed by repeated measurements for 15–20 yrs. Growth levels predicted by the models were calibrated using NFI11 data to remove bias originating from the sample of the modelling data. The mixed linear models technique was used in model estimation. The models will be incorporated into the MOTTI stand simulator to replace the current peatlands growth models.

Mistletoe-induced growth reductions at the forest stand scale.

The hemiparasite European mistletoe (Viscum album L.) adversely affects growth and reproduction of the host Scots pine (Pinus sylvestris L.) and in consequence may lead to tree death. Here, we aimed to estimate mistletoe-induced losses in timber yield applying the process-based forest growth model 4C. The parasite was implemented into the eco-physiological forest growth model 4C using (literature-derived) established impacts of the parasite on the tree's water and carbon cycle. The amended model was validated simulating a sample forest stand in the Berlin area (Germany) comprising trees with and without mistletoe infection. At the same forest stand, tree core measurements were taken to evaluate simulated and observed growth. A subsample of trees were harvested to quantify biomass compartments of the tree canopy and to derive a growth function of the mistletoe population. The process-based simulations of the forest stand revealed 27% reduction in basal area increment (BAI) during the last 9 years of heavy infection, which was confirmed by the measurements (29% mean growth reduction). The long-term simulations of the forest stand before and during the parasite infection showed that the amended forest growth model 4C depicts well the BAI growth pattern during >100 years and also quantifies well the mistletoe-induced growth reductions in Scots pine stands.

Temperature and soil fertility as regulators of tree line Scots pine growth and survival-implications for the acclimation capacity of northern populations.

The acclimation capacity of leading edge tree populations is crucially important in a warming climate. Theoretical considerations suggest that adaptation through genetic change is needed, but this may be a slow process. Both positive and catastrophic outcomes have been predicted, while empirical studies have lagged behind theory development. Here we present results of a 30-year study of 55,000 Scots pine (Pinus sylvestris) trees, planted in 15 common gardens in three consecutive years near and beyond the present Scots pine tree line. Our results show that, contrary to earlier predictions, even long-distance transfers to the North can be successful when soil fertility is high. This suggests that present northern populations have a very high acclimation capacity. We also found that while temperature largely controls Scots pine growth, soil nutrient availability plays an important role-in concert with interpopulation genetic variation-in Scots pine survival and fitness in tree line conditions. These results suggest that rapid range expansions and substantial growth enhancements of Scots pine are possible in fertile sites as seed production and soil nutrient mineralization are both known to increase under a warming climate. Finally, as the ontogenetic pattern of tree mortality was highly site specific and unpredictable, our results emphasize the need for long-term field trials when searching for the factors that control fitness of trees in the variable edaphic and climatic conditions of the far North.

Effects of Reforestation and Site Preparation Methods on Early Growth and Survival of Scots Pine (Pinus sylvestris L.) in South-Eastern Poland

Successful tree regeneration is a key process in ensuring forest sustainability and one of the most crucial investments made in silviculture. This study compared the effects of three reforestation methods (planting, direct seeding, and natural regeneration) and three mechanical site preparation methods (double mould-board forest plough (FP); active plough (AP); and forest mill (FM)) on biometric parameters, survival, and density of Scots pine (Pinus sylvestris L.) seedlings in the first 4 years of growth in a clear-cut area in south-eastern Poland. Planted seedlings were higher, thicker in root collar, and had higher survival rates after the fourth growing season than trees from natural regeneration and direct seeding. Site preparation methods did not affect the density of planted seedlings. After natural regeneration and direct seeding, seedling density was lower and less homogeneous (plots with no seedlings) in FM soil preparation in comparison to other methods. The survival of pines in all reforestation methods was not affected significantly by site preparation methods. Our results indicate that the best mechanical site preparation method for planting is FM, as this is the one that least disturbs the soil environment. For direct seeding the best results were achieved after AP preparation. Natural regeneration of Scots pine was most effective after FP use, and in relatively wet years also after AP use.

Effects of precipitation and temperature on the growth variation of Scots pine—A case study at two extreme sites in Finland

Site properties have received limited attention in analyzing the weather-growth relationship of trees. We analyzed the annual growth variation of Scots pine on two extreme sites in southern Finland: a dry hill top site and a moist patch of mineral soil surrounded by a large peatland. The effects of daily precipitation and temperature were related to growth variation using correlation analyses. In addition, the common signal and the difference of ring-width indices from the dry and moist sites were studied via principal component analysis and related to the daily weather measurements. All possible time intervals longer than 14days from current year April 1st to August 31st were tested. We also modeled daily photosynthetic production of Scots pine using two parameter sets, one describing limited stomatal closure and the other one easily triggered stomatal closure. Growth variation at the dry site was linked with variation of precipitation during early and middle parts of growing season, while growth at moist site was correlated with temperature during the middle part of growing season. Daily photosynthetic production, modeled with parameters describing mostly open stomata produced a rather strong negative correlation with ring-width indices from the dry site, possibly indicating that the parametrization overestimated growth during dry years. Other than that, the modeled photosynthetic production was relatively weakly correlated with the ring-width indices. Evidently, the mechanisms controlling Scots pine growth at drought-sensitive sites in southern Finland are complex. Overall, the results indicate that site properties, especially water retention capacity, need to be considered in dendroecological research.